let userName = process.argv[2];
let pwd = process.argv[3];
let userInfor = userName + ":" + pwd;
//得到buffer实例
let buf = Buffer.from(userInfor, "utf-8");
console.log(buf);
//转换成base64字符串
let base64str = buf.toString("base64");
//编码转换是可逆的
console.log(base64str)

